116 CANADIAN FOSSILS. 
not before known in forms of this kind, and suggests the possibility, if not 
the probability, that some others of the bi-celluliferous or diprionidian forms 
may have grown with this compound arrangement of the parts. 
The stipes of the specimen figure 9, if separated, present an aspect very 
analogous to those of Diplograptus and Retiolites, and would not be sup- 
posed to have had any different mode of growth. ‘The setiform processes 
at the base of some of the species may be regarded as an objection to the © 
compound mode of growth; but this feature would offer a still greater 
objection to regarding those stipes as simple, and as having grown from an 
independent radix. The three species of the genus now known to me, 
present some important points of difference one from the other, and there 
still remains some obscurity regarding the arrangement of the cellules. 
These forms are nearly related to the Retiolites of Barrande ; but the 
-texture of the specimens examined, and the arrangement of the parts, 
differ so much from authentic specimens of A. Geinitzianus, that I have 
separated them under the above designation. 
RETIOGRAPTUS TENTACULATUS, Hall. 
Plate XIV, figures 6-8. 
(GRAPTOLITHUS TENTACULATUS : (Genus Retiolites, Barrande) Geological Survey of Canada, 
Report for 1857, p. 134.) 
Description.—Original form of the entire frond unknown. Stipes simple, 
narrow, very elongate-elliptical when entire, narrower at the base, and 
gradually expanding above to the middle of their length; where they attam 
the greatest width, and become gradually narrower above, with the apex 
obtuse or rounded. 
Central axis strong and well defined, extending beyond the stipe a dis- 
tance equal to half its length: base furnished with two elongate diverging 
sete, which extending from the outer edges, gradually curve down- 
wards, and finally assume a direction nearly parallel to the axis. Within 
these long outer processes, and proceeding from the centre of the base of 
the stipe, there is an extension of the filiform axis, which sometimes appears 
in its duplicate character. 
Exterior margins reticulate, furnished with a row of hexagonal meshes, 
separated by slender processes extending from the substance of the stipe, 
which unite in a continuous filiform border; from this proceed, at about 
every second reticulation, short setiform spines, which in the middle of 
the length of the stipe are rectangular to the axis, while nearer to the base 
